* without prior notice.
 *
 */
public class ExtensionDescriptor {

    private List<String> exportedPackages;

    private List<String> exportedArtifacts;

    ExtensionDescriptor() {
        // hide constructor
    }

    public List<String> getExportedPackages() {
        if (exportedPackages == null) {

        }

        return extensionDescriptor;
    }

    /**
     * @since 3.3.0
     */
    public ExtensionDescriptor build(InputStream is) throws IOException {
        ExtensionDescriptor extensionDescriptor = new ExtensionDescriptor();

        XmlNode dom;
        try {
            XMLStreamReader reader = XMLInputFactory.newFactory().createXMLStreamReader(is);
            dom = XmlService.read(reader);

import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.maven.api.xml.XmlNode;
import org.apache.maven.project.ExtensionDescriptor;
import org.apache.maven.project.ExtensionDescriptorBuilder;
import org.codehaus.plexus.classworlds.realm.ClassRealm;

/**

    }

    /**
     * CacheRecord
     */
    class CacheRecord {

        private final ClassRealm realm;

        private final ExtensionDescriptor descriptor;

        private final List<Artifact> artifacts;

        CacheRecord(ClassRealm realm, ExtensionDescriptor descriptor, List<Artifact> artifacts) {
            this.realm = realm;
            this.descriptor = descriptor;
            this.artifacts = artifacts;

    @Override
    public CacheRecord get(Key key) {
        return cache.get(key);
    }

    @Override
    public CacheRecord put(
            Key key, ClassRealm extensionRealm, ExtensionDescriptor extensionDescriptor, List<Artifact> artifacts) {
        Objects.requireNonNull(extensionRealm, "extensionRealm cannot be null");

        if (cache.containsKey(key)) {

            final ExtensionDescriptor extensionDescriptor = recordRealm.getDescriptor();
            final List<Artifact> artifacts = recordRealm.getArtifacts();

            extensionRealms.add(extensionRealm);
            if (extensionDescriptor != null) {
                exportedPackages.put(extensionRealm, extensionDescriptor.getExportedPackages());

        return new ByteArrayInputStream(xml.getBytes(StandardCharsets.UTF_8));
    }

    @Test
    void testEmptyDescriptor() throws Exception {
        String xml = "<extension></extension>";

        ExtensionDescriptor ed = builder.build(toStream(xml));

        assertNotNull(ed);
        assertNotNull(ed.getExportedPackages());
        assertTrue(ed.getExportedPackages().isEmpty());
        assertNotNull(ed.getExportedArtifacts());

  xsi:schemaLocation="http://codehaus-plexus.github.io/MODELLO/2.0.0 https://codehaus-plexus.github.io/modello/xsd/modello-2.0.0.xsd">
  <id>extension</id>
  <name>ExtensionDescriptor</name>
  <description><![CDATA[
    Extension descriptor, stored in <code>META-INF/maven/extension.xml</code> in an extension's jar artifact to

                }
            }

            discoverPluginComponents(extensionRealm, plugin, pluginDescriptor);

            ExtensionDescriptor extensionDescriptor = null;
            Artifact extensionArtifact = artifacts.get(0);
            try {
                extensionDescriptor = extensionDescriptorBuilder.build(extensionArtifact.getFile());
            } catch (IOException e) {